Do NOT say "coach i saw him step on him but he was still trying to occupy third base and did not make an attempt to go home." All of that phrasing makes it sound like you had OBS and opens the door for discussion. Keep the focus on "it was NOT OBS" and keep the discussion to about 10 seconds.
Hmm ... (and, no, I do not disagree in reality -- just another error in the book -- the definition section contains the proper wording) (2) He is touched by a pitched ball which he is not attempting to hit unless (A) The ball is in the strike zone when it touches the batter, or (B) The batter makes no attempt to avoid being touched by the ball; (2) If the ball is in the strike zone when it touches the batter, it shall be called a strike, whether or not the batter tries to avoid the ball. If the ball is outside the strike zone when it touches the batter, it shall be called a ball if he makes no attempt to avoid being touched.
1) Yes, it doesn't matter, assuming I saw the pitch. 2) There's not such thing as a "marginal pitch."
IMO, some of us (and I'm not necessarily implying that this is you, jkumpire) have gone way overboard on the "the way the catcher catches the pitch matters."
As I like to teach it, "I try very hard not to let the catcher fool me. But, I'm not dumb enough to think that it doesn't happen. And, a catcher can fool me into striking a ball or into balling a strike."
It seems to me that this is "nothing" and that's what you should have called.
*IF* F5 stayed on R2 for any period of time, then the proper call would be OBS and you should award whatever base you think R2 would have obtained absent the OBS. That might be third, it might be home. Whether R2 attempted to reach home can help you decide what would have happened, but it isn't required that he try for home for you to award it.
(And, your conversation with the coach shouldn't go "back and forth."
Does it need an interpretation? the rule seems pretty clear to me (with the possible exception that it says "professional leagues" and most of us don't work a lot of "professional league" ball):
(l) (8.06) Visits to the Mound A professional league shall adopt the following rule pertaining to the visit of the manager or coach to the pitcher:
(1) This rule limits the number of trips a manager or coach may make to any one pitcher in any one inning; (2) A second trip to the same pitcher in the same inning will cause this pitcher’s automatic removal from the game; (3) The manager or coach is prohibited from making a second visit to the mound while the same batter is at bat, but (4) if a pinch-hitter is substituted for this batter, the manager or coach may make a second visit to the mound, but must remove the pitcher from the game. A manager or coach is considered to have concluded his visit to the mound when he leaves the 18-foot circle surrounding the pitcher’s rubber. Rule 5.10(l) Comment (Rule 8.06 Comment): If the manager or coach goes to the catcher or infielder and that player then goes to the mound or the pitcher comes to him at his position before there is an intervening play (a pitch or other play) that will be the same as the manager or coach going to the mound. Any attempt to evade or circumvent this rule by the manager or coach going to the catcher or an infielder and then that player going to the mound to confer with the pitcher shall constitute a trip to the mound. If the coach goes to the mound and removes a pitcher and then the manager goes to the mound to talk with the new pitcher, that will constitute one trip to that new pitcher that inning. A manager or coach shall not be considered to have concluded his visit to the mound if he temporarily leaves the 18-foot circle surrounding the pitcher’s rubber for purposes of notifying the umpire that a double-switch or substitution is being made. In a case where a manager has made his first trip to the mound and then returns the second time to the mound in the same inning with the same pitcher in the game and the same batter at bat, after being warned by the umpire that he cannot return to the mound, the manager shall be removed from the game and the pitcher required to pitch to the batter until he is retired or gets on base. After the batter is retired, or becomes a base runner, then this pitcher must be removed from the game. The manager should be notified that his pitcher will be removed from the game after he pitches to one hitter, so he can have a substitute pitcher warmed up. The substitute pitcher will be allowed eight preparatory pitches or more if in the umpire’s judgment circumstances justify.
I will point out that it's a mechanic that can be useful but you don't need to use it all the time. Had a play today where I didn't use it -- didn't need to. Partner had a play where he didn't need to use it but he did. Came across as "no s***" -- much like yelling "foul ball" on a ball over the backstop, etc.
(And, none of that is directed at Majordave, just a caution to all)
I don't think you need to see the back end of the play (to decide on interference). *IF* it's an illegal slide (*If* the spikes are too high), then two are out since this was during a force play.. *IF* this was not an illegal slide, then play on.
As you pointed out, A (beyond the base) and B (to the side) are probably illegal slides in FED regardless of the spike issue, and B is also iprobably illegal in NCAA (although we could use more description in the OP). Again, no need to see the back end on these.